J. Anim Sci., doi: 10.2527/jas.2006-379
©Copyright, 2006, The American Society of Animal Science
The CHRNE 470del20 mutation causing congenital myasthenic syndrome in South African Brahman cattle: prevalence, origin, and association with performance traits
P. N. Thompson 1*,
J. H. J. van der Werf 2,
J. A. P. Heesterbeek 3,
J. A. M. van Arendonk 4
1 Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa
2 School of Rural Science and Agriculture, University of New England, Armidale, Australia
3 Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, the Netherlands
4 Animal Breeding and Genetics Group, Wageningen University, the Netherlands
* To whom correspondence should be addressed. E-mail: peter.thompson{at}up.ac.za.
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Abstract |
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Genotyping of the South African registered Brahman cattle population for the 470del20 mutation in the CHRNE gene causing congenital myasthenic syndrome (CMS), was carried out in 1,453 animals. Overall prevalence of carriers was 0.97% (95% confidence interval 0.50% to 1.68%). Carrier prevalence among breeding bulls in 2004 was 1.22% (95% confidence interval 0.65% to 2.15%), and had not changed significantly since 2000. Using segregation analysis, CMS genotype probabilities were calculated for all 612,219 animals in the pedigree, leading to the identification of 2 founder animals as the most likely original carriers. Pedigree analysis revealed no ancestors common to all known carriers, but that the mutation had been introduced at least twice into the South African Brahman population, probably via animals imported from the U.S.A.. The effects of CMS genotype probability on adjusted birth, 200-d, 400-d, and 600-d weights, as well as on EBV for birth, 200-d, 400-d, and 600-d weights, and milk, were estimated, accounting for effects of sire. Heterozygosity for the CHRNE 470del20 mutation was associated with a 13.3 kg increase in adjusted 600-d weight (P = 0.03). Positive effects of CMS carrier status on all weight EBV were found, but no effect was found on milk EBV. We conclude that CMS carriers have a weight advantage at 600 d, and possibly also at birth, 200 d, and 400 d. This may confer a selective advantage and tend to increase the frequency of the mutation.
Key Words:
Brahman cattle, congenital myasthenic syndrome, genotyping, heterozygote, pedigree analysis
